1. Field of the Invention
The present invention generally relates to a recording medium such as a compact disc and, more particularly, to a recording medium for storing information to be protected from an unauthorized access.
2. Description of the Related Art
In recent years, portable optical discs having a large capacity have become popular as a recording medium used with a personal computer. A read only type compact disc (CD-ROM) has become very popular. A recordable compact disc (CD-R) or a rewritable compact disc (CD-RW) is a typical recordable recording medium used with a personal computer.
In many cases, information recorded on a recording medium such as a CD-R or a CD-RW is created by the owner of the recording medium so as to be used by the owner or limited persons authorized by the owner. Additionally, in some cases, information recorded on the recording medium contains very important contents such as secret business information. Thus, a damage due to lost of such a recording medium or an unauthorized access to such a recording medium is inestimable.
Additionally, it has become important to protect information recorded on a CD-ROM from an illegal copy in light of copyright.
Accordingly, various techniques have been suggested to prevent illegal use of such a recording medium. In order to prevent an illegal access to information (programs or data) recorded on a recording medium or an illegal copy of such information, Japanese Laid-Open Patent Applications No.5-257816 and No.6-295521 disclose protecting methods using a licensing key (individual number key) or an enciphering technique.
Additionally, Japanese Laid-Open Patent Applications No.11-134650, No.11-134719 and No.11-134813 suggest measures taken for a recording method of a recording medium or a recording and reproducing apparatus.
However, practically in a data processing apparatus such as a personal computer using an operating system, there are many cases in which a recording medium is mounted on an apparatus. In this case, the term “be mounted on” means that a recording or reproducing operation with respect a recording medium can be performed through a drive apparatus due to predetermined information (for example, root directory information defined as a normal file system) recorded at a predetermined position of the recording medium. That is, an access can be made to information recorded on a recording medium by controlling the drive apparatus for reading or writing the recording medium. Thus, the above mentioned methods using the licensing key or enciphering technique are not so effective. Additionally, enciphered information may be illegally used by analyzing the enciphering algorithm.
On the other hand, if the measures suggested in Japanese Laid-Open Patent Applications No.11-134650, No.11-134719 and No.11-134813 are to be taken, such measures cannot be applied to recording and reproducing apparatuses that are already on the market. Thus, such measures must be applied to a new apparatus, and there needs a time to introduce such a new apparatus into the market.